1. Field of the Invention
The present invention relates to a projection lens and a projection device thereof, and more specifically, to a projection lens having a short throw function and a projection device thereof.
2. Description of the Prior Art
With development of technology, a projection device has been commonly used for presenting image information in a meeting. Due to limited space of a meeting room, a projection device having a projection lens with an ultra-short focal length is widely applied to image projection since it is convenient to carry as well as easy to adjust its focus. A conventional lens mechanism of short throw projectors is composed of two lens groups including five lenses. In this design, one lens group close to a projection screen has a negative diopter for diverging light, and the other lens group away from the projection screen has a positive diopter for converging light. However, this design usually needs to utilize an aspherical lens with a high cost to eliminate lateral color aberration of light, so as to greatly increase the manufacturing cost of the short throw lens mechanism. Thus, how to reduce the manufacturing cost of the short throw lens mechanism and further eliminate lateral color aberration of light is one of the major issues in the optical lens industry.